Need input: Diagnosing and repairing failed LEDs

[llebcire]

All,

I'm looking for advice on how to diagnose and repair a failed LED.

I have a pair of Chinese LEDs, from Reef Radiance but no different than other varieties on eBay, and this week I lost the actinic channel on one of the fixtures. I've been able to troubleshoot down to the actual LEDs by swapping components and here's where I need input:

Typically, are the LEDs wired in series so a failure takes out the channel? My assumption is either a failed connection, possible although the lights are never moved, or a failed diode which seems much more likely.

I do have a digital multi-meter which I could use to test, but if they're in series what's the harm in using a jumper over each LED to test and when the failed one is found the lights should come on?

When I find the failed LED, is there a danger in using a jumper to bypass it? I realize, if they are in series, this changes the electrical load slightly but with 22 LEDs it wouldn't be much variance. As I'm planning on breaking the tank down in the next week or so I'm looking for options.

Thoughts?

I look forward to your feedback!

-Eric

 

[oreo57]

Unplug the light.. Put VOM either on diode or low Ohms.
Test each LED by putting plus on plus pad neg.. ect..for each ind. diode.. Good ones should dimly light..

You probably can bridge around the bad one or 2 BUT only if drivers are constant current (should be) and your remaining diode voltages do not go below the min. of the driver..Should be posted like 52-70V DC or such..

 

[llebcire]

Thank you!

I can test the diodes without removing?

Sent from my SM-G930R4 using Tapatalk

 

[llebcire]

Here's what I have.

Sent from my SM-G930R4 using Tapatalk

 

[oreo57]

Thank you!

I can test the diodes without removing?

Sent from my SM-G930R4 using Tapatalk

Yes but unplug it of course..and you need to match the polarity..

 

[oreo57]

Here's what I have.

Sent from my SM-G930R4 using Tapatalk

Looks like you have 21 diodes in series for that channel..
Assuming a V(f) at 530mA of say 3.5V per diode = 73.5V

Point is driver could act wonky if the cumulative V(f) falls below 70V..
so jumping over more than one diode may be problematic..

 

[llebcire]

Thanks again for your help. Your explanation makes it easy to understand and I should be okay bypassing one diode but any more could get wonky and of course I'll want to replace the defective LED.

-Eric

Sent from my SM-G930R4 using Tapatalk

 

[llebcire]

Thanks for your help oreo57.

These are easy to diagnose with a multimeter but several, while working, don't look good.

Guessing I need to determine whether I want to replace the entire actinic channel (21) or replace the entire light.

-Eric

Sent from my SM-G930R4 using Tapatalk